Manufacture of pistons



Dec. 9, 1952 LfsuLPRlzlo 2,620,530

MANUFACTURE OF PISTONS Filed Jun a, 1950 2 swam-41mm 1 F I r51 -El:INVEN pace/A2 521/ r/ BY 64M! 0 ATTO/Q/Yi) D 9, 1952 L. SULPRIZIO2,620,530

MANUFACTURE OF PISTONS Filed June 8, 1950 2 SHEETS-SHEET 2 IINVENTOBU[we/m 54/ r/z/v BY I,

in) a- Patented Dec. 9, 1952 MANUFACTURE or PISTONS Lucelio Sulprizio,Castro Valley, Calif., assignor to United Engine & Machine 00., acorporation of California Application June 8, 1950, Serial No. 166,900

1 Claim. 1

This invention relates to the manufacture of pistons and the like andparticularly to pistons made of aluminum or an aluminum base alloy andwhich are employed in engines which operate, for example, on the Otto ordiesel cycle. In accordance with this invention, such a piston is castin a mold with a concentric metal ring which forms a portion of theworking side wall of the piston. The ferrous metal ring is first coatedwith a thin iron-aluminum alloy as by immersion in a suitable bath atabout 1525 to about 1625 F. for a short time, as is taught in theWhitfield et a1. Patents 2,396,730 and 2,455,457. Immediately after thecoating is applied and before the ring has cooled, the ring istransferred to a mold and the piston is cast; the ferrous metal ring isintegrally bonded to the body of aluminum or aluminum alloy forming thepiston. When the mass has cooled, the surfaces of the piston aresuitably machined, a groove being cut in the ferrous metal ring toprovide a support for a piston ring. If desired, the ferrous metal ringcan be provided of such size as to carry several piston rings. If onlyone ring is provided, the groove is cut at the head end or top of thepiston and is utilized to provide support for the top ring. Theprovision and. maintenance of an adequate seal about the top of thepiston has long been recognized as essential to long engine life andhigh operating efficiency; imperfect or worn grooves and lands enablecombustion gases to destroy compression factors, shorten ring life,carbonize and freeze rings with resultant cylinder wear and fuel waste.Each of these is obviated or reduced by utilizing a piston embodying andmade in accordance with this invention.

It is in general the broad object of the present invention to provide anovel and improved process for the manufacture of a piston including anintegrally bonded ferrous metal in the peripheral surface of the piston.

A further object of the invention is to provide a novel mold for thecasting of a piston having an integrally bonded concentric ferrous metalring which forms a part of the side-wall working surface of the piston.

The invention includes other objects and features of advantage, some ofwhich, together with the foregoing, will appear hereinafter wherein thepreferred practice of the method and the preferred form of moldembodying this invention are disclosed.

In the drawing accompanying and forming a part hereof,

Figure 1 is a schematic side elevation of a mold and core, portions ofthe mold and core being cut away to illustrate their relation to oneanother in preparation for completion of the mold prior to the castingoperation.

Figure 2 is a diagrammatic view illustrating the flow of metal in theform of mold shown in Figure 1.

Figure 3 is a diagrammatic View illustrating the flow of metal inanother form of mold embodying the present invention.

Figure 4 is a sectional view illustrating the construction of one formof a machined piston produced in accordance with this invention.

Figure 5 is a side elevation of a piston, partially in section, asremoved from the mold of this invention.

Figure 6 is a plan view of the piston in Figure 5.

Referring to the drawings, this invention particularly relates to themanufacture of a piston. generally indicated at 6 and having one or moregrooves 1 therein for the reception of suitable piston rings. It ispreferred that at least one of these grooves, preferably the uppergroove, include an integrally bonded annular ring 8 of ferrous metal inthe piston side-wall working surface. To ensure good results, thealuminum or aluminum base alloy piston structure and the ferrous metalring must be integrally bonded through a ferro-aluminum alloy. This isattained by first heating the surface of the ring to a temperature andfor a time sufficient to form a ferroaluminum alloy film on the surfaceof the article, after which, and without cooling, the coated ring ispositioned in the mold and the piston is cast. The conditions forformation of the alloy film and the general process details aredisclosed in the aforementioned patents.

In accordance with this invention, the aluminum coated ferrous metalring is supported in such relation to the mold that it is completelyembedded in the aluminum metal, as is shown in Figures 5 and 6, andexcess metal must Joe removed as by machining to exhibit the ring andprior to formation of the groove 9 therein, as in Figure 4. Thus,referring particularly to Figure 1, I have indicated a mold generally at2| and having a cylindrical mold cavity for formation of a piston; themold has a conventional gate 22 through which the molten metal isadmitted to the :bottom of the mold. A suitable core, indicatedgenerally at 23, is placed in the mold, cover 24 being adapted to fitthe top of the mold and including a riser 3| completing the mold.

In accordance with this invention, the mold and cover are each providedwith an annular recess 26 havin a diameter larger than that of thepiston proper, the recess being at an elevation in the moldcorresponding to that of the position of the ferrous metal ring in thepiston. The recess is of a size to receive the ferrous metal ring andretain it in a spaced relation to the adjacent side wall of thecompleted mold. At spaced points about the annular recess 26 in each ofthe mold proper and the cover, the recess is discontinuous and the sidewall is continued as is indicated at 21, a notchor recess 28 beingprovided in each such continuation 21 to provide a support forthealuminum coated ferrous metal ring. Preferably, at least three suchsupports are used to ensure centering of the ring. The notches inthecoverandin the mold are preferably offset so that a minimum area ofthe ring is sealed against the wallon either side of the ring (seeFigures and 6). Thus, except at the places where the ring 'is engagedwith the notches 28, it will be supported in a freely spaced relation tothe wall .21 :of the mold and metal can flow ,freely up-and around thering, as has been .-indicated in *Figure 2. Slag and oxide are thusforced into the "riser 3| and do not collect in and around the ring atits junction with-the wall, asis the case when the ring is-merelysupported at-the desiredxelevation within the mold with its outersurface in engagement with the cylindrical :surface of the mold; thecompletepiston-after casting is shown in Figures 5 and-6 andywhentypically machined, in Figure 4.

The invention-can be practiced with a mold of the type illustrated inFigure 3 wherein-core 4| dependsiinto the mold and the ferrous-metalring 42 is supported, as has been described, in the bottom portion'ofthe mold. 'The metalithen flows up and around the ring from gate 4-3, asis indicated by the arrow, the slag and oxide collecting in the upperportion of the piston about-the skirt portion where its presence is'notto undesirable.

A typical cast piston is shown in'Figures 5'and 6, with the excess metalcompletely surrounding the ferrous-metal ring except for thoserelatively small areas wherethe ring is supported in position in themold. This excess metal is readily removed in the machining operation.In this manner, an improved piston structure is provided whereintheconcentric ferrous metal ring utilized as a piston ring support isadequately bonded by a ferro-aluminum bond to the piston. One can useany desired ferrous metal for the ring which is suited to the use of thepiston.

Because of the very limited contact of the hot alloyed ring with theouter mold, the ring retains its heat and; metal flowing'overzand aroundit does=not=cool appreciably. This "same result can be achieved byproviding three or more conical indentations in the surface of the ringand spaced .equally about the periphery to receive the pointed end of apin-like support which :projectsfrbni the'mold wall, one of the threepinsb'eing spring-biased to hold the ring against the other two pinswhich are fixed. Because of the small area of contact between the pins,the heat loss through the pins is negligible.

I-claim:

In the casting of analuminum piston having an :annular iron ringsupported concentrically thereon, the steps 'of coating an .iron .-ringwith an iron-aluminum alloy by immersing the ring for ashort time in amolten bath-of said alloy at a bath temperature of from about l525 toabout 1-625" F. and immediately thereafter supporting" the -hotring in amold for'ithe ipiston at a plurality of spaced points about theperiphery of the ring with the ri-ng;.outer wall spaced from andconcentric with the -mold to provide a free-passageway for -metal howbetween the rmold and the ring -outer -wall, and then, while theringisstill'hot, pouring 'a molten metal of the class consisting .ofaluminumaand aluminum base alloys intothe mold to ifill the mold andembed said ring 1 therein.

LUCELIO SULPRIZIO.

REFERENCES CITED The following references are of "record in the file ofthis patent:

UNITED STATES PATENTS Number Name 7 Date 1,931,587 McConnel.. Oct. '24,1933 2,052,921 'Dockrayet a1. Sept. .1, .1936 2,369,067 Mayer v ep. 1915 2,396,730 Whitfield Mar. 19,1946

FOREIGN PATENTS I Number Country 7 Date 401,996 Germany ISept. 11.1924

